What’s the best way to measure the depth of a well using a smartphone? If you’re fed up with social media, you might kill two birds with one stone and drop the thing down the well and listen for the splash. But if you’re looking for a less intrusive — not to mention less expensive — method, you could also use your phone to get the depth acoustically.
This is a quick hack that [Practical Engineering Solutions] came up with to measure the distance to the surface of the water in a residential well, which we were skeptical would work with any precision due to its deceptive simplicity. All you need to do is start a sound recorder app and place the phone on the well cover. A few taps on the casing of the well with a hammer send sound impulses down the well; the reflections from the water show up in the recording, which can be analyzed in Audacity or some similar sound editing program. From there it’s easy to measure how long it took for the echo to return and calculate the distance to the water. In the video below, he was able to get within 3% of the physically measured depth — pretty impressive.
Of course, a few caveats apply. It’s important to use a dead-blow hammer to avoid ringing the steel well casing, which would muddle the return signal. You also might want to physically couple the phone to the well cap so it doesn’t bounce around too much; in the video it’s suggested a few bags filled with sand as ballast could be used to keep the phone in place. You also might get unwanted reflections from down-hole equipment such as the drop pipe or wires leading to the submersible pump.
Sources of error aside, this is a clever idea for a quick measurement that has the benefit of not needing to open the well. It’s also another clever use of Audacity to use sound to see the world around us in a different way.
slightly related: I used audacity to measure the switching time of a on/on switch by shorting (ok, with current limiting resistor) the mic-in with both switch-contacts parallel, which gave a relatively nice and reasonably repeatable rectangle signal with a width of about 2 ms for every flick
Used to record the sound of a passing object (e.g., an RC plane) and then estimate its speed using Audacity to measure the doppler shift. Now there are apps for that.
Hehe. I taught my teacher how to measure the speed of passing cars that way with only his ears. He was a good musician and had an uncannily accurate pitch estimator built-in. He could judge the pitch shift, and just needed a way to convert that into speed. He was my math teacher, so I suspect the exercise was mostly for my benefit, but he seemed genuinely appreciative when I showed him how to convert centitones to miles per hour.
I use an app called Phyphox that has a built in sonar. It also has tons of other useful tools using sensors that most smartphones have.
I definitely recommend checking it out.
Funny story: A guy I used to work with had a family business that made wood dipsticks to measure fuel depth in buried tanks — you know, the ones at pretty much every gas station.
He was a trained electronics technologist and figured he’d reinvent the business and make a killing by making an “acoustic dipstick”: a cap for the tank that just pinged the surface of the fuel and measured the distance, making a readout in the office. No trudging out to the tank to make a measurement, no replacing broken dipsticks. Should be a slam dunk, right? Especially with the customer rolodex already in hand.
After going through all the explosive atmosphere intrinsically-safe stuff he had a working product, but couldn’t sell any. Nobody would trust it. Because a wood dipstick can’t lie.
Now you see them all the time as stream height gauges, suspended under bridges. And his company still makes wood dipsticks.
I’m kind of surprised the acoustic ones didn’t sell. It sounds pretty annoying to do by hand considering that there’s probably lots of gas fumes involved and then you have a probably dripping dipstick full of gas to deal with.
Long time reader, first time commentary: there is an open source android app called phyphox that has an acoustic distance measurement tool that is actually really accurate!
Time domain reflectometry in acoustic form.
Also known as sonar!